DiskSpy is a software disk LED which shows disk reads and writes in menu bar.

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DiskSpy 1.5 (August 28, 2009)

Copyright 2002-2009 Nick Zitzmann.

What is DiskSpy?

While many PC makers put hard disk LEDs on the outside of their computers, Apple hasn't put any disk LEDs on any Macintoshes since the SE/30. Some Mac old-timers may remember the number of products that were available during the System 7 era that provided a software disk LED in the menu bar. (Software Santa Does!)

DiskSpy is a small program that acts as a software disk LED for Macs running Mac OS X. DiskSpy sits in the menu bar and gives visual notifications when the OS is reading from or writing to a disk. DiskSpy does not run in the kernel region, does not use any private frameworks or undocumented APIs, does not require any hacks to use, does not trap any low-level I/O calls, does not run as the super user, nor does it actually write to any disk(s) except to save its preferences, so it is safe to use. And the icons can be customized.

WARNING! DiskSpy does consume CPU time continuously. If you are using DiskSpy on a portable Mac (i.e. a PowerBook, iBook, or MacBook), and it is running off the battery, then you must not use this program if you value the life of your battery. Also, if you are running a CPU intensive task, such as compiling, rendering, serving large amounts of network data, or playing a computer game, then you may want to quit running DiskSpy for a while to save CPU cycles.

DiskSpy is freeware. However, if you like it, I would greatly appreciate it if you would evaluate and consider purchasing a license for one of my other fine Macintosh products (DiskSpy Solid, DropPrint, HenWen, etc.). You can see my public software portfolio at:http://seiryu.home.comcast.net/

Using DiskSpy

Applications don't get much simpler than this, folks. All you need to do is copy DiskSpy to any place on any disk and run it. The Applications folder is acceptable, but DiskSpy can run in any other place without any problems. A little disk icon will appear in the status bar that shows the status of all your disks.

Idle: If your system is idle, then you will see what looks like two clear LEDs in the menu bar.

Read: If something is reading data from one of your drives, then the left LED will turn green, indicating that data is being read from your disk into RAM.

Write: If something is writing data to one of your drives, then the right LED will turn red, indicating that something in RAM is being saved to a disk.

Both: You may also see both lights come on, which means separate read and write operations were done close to simultaneously.

To adjust DiskSpy's CPU usage, among other things, see "DiskSpy's Preferences" below.

To stop DiskSpy, all you need to do is click on the disk icon and choose "Quit DiskSpy". That's all there is to it!

DiskSpy's Preferences

There are a couple of options you can set with DiskSpy. Select "Preferences" from DiskSpy's menu to bring up a window that offers the following options:

DiskSpy's Update Timing: By default, DiskSpy updates once every 90,000 microseconds, and DiskSpy Solid updates once every 120,000 microseconds. To adjust DiskSpy's update timing, bring up the preferences window. A window with a slider will appear. You can use the slider here to adjust how often DiskSpy updates. If you move this slider to the right, the pace of updates will slow down, which makes DiskSpy consume less CPU time, but the icons will be drawn at a slower rate. If you move it to the left, the pace of updates will increase, which makes DiskSpy more hyper, but it consumes more CPU time. You can monitor DiskSpy's CPU usage by using either ProcessViewer, the Top command line program, or various other CPU monitor programs.

You can set DiskSpy's update time to 15,000 microseconds or less, but at short times like these, DiskSpy will monopolize the CPU, which will cause your Mac's overall performance to seriously suffer. Try to set a value that makes DiskSpy update fast enough for you but does not drain your CPU. Changes for this setting take place immediately when clicking on the OK button.